Methods and materials for treating cancer

ABSTRACT

This document provides methods and materials related to treating cancer. For example, methods and materials for using nucleic acid libraries to treat cancer are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371and claims benefit of International Application No. PCT/US2011/024397,having an International Filing Date of Feb. 10, 2011, which claims thebenefit of U.S. Provisional Application Ser. No. 61/303,222, filed Feb.10, 2010. The disclosures of the prior applications are considered partof (and are incorporated by reference in) the disclosure of thisapplication.

BACKGROUND

1. Technical Field

This document relates to methods and materials involved in treatingcancer. For example, this document provides methods and material forusing nucleic acid libraries to treat cancer.

2. Background Information

Cancer is a serious illness that affects many people every year. Ingeneral, there are several common methods for treating cancer: surgery,chemotherapy, radiation therapy, immunotherapy, and biologic therapy.When initially diagnosed with cancer, a cancer specialist such as anoncologist can provide a patient with various cancer treatment options.Typically, an oncologist will recommend the best treatment plan based onthe type of cancer, how far it has spread, and other important factorslike the age and general health of the patient.

SUMMARY

This document provides methods and materials related to treating cancer.For example, this document provides methods and materials for usingnucleic acid libraries to treat cancer. As described herein, a nucleicacid library can be used to deliver a large number of the antigens(e.g., polypeptides) that are present in the particular cancer, or inthe organ or tissue of origin of the cancer, to a mammal such that themammal's immune system can develop an immune response against thoseantigens (e.g., polypeptides) that are expressed by the cancer, therebycausing the cancer to regress. For example, a cDNA expression librarydesigned to express polypeptides from a particular cancer, or the organor tissue of origin of the cancer, can be engineered into viruses (e.g.,an oncolytic virus), and then the engineered viruses can be administeredto a patient such that the polypeptides are expressed. This ensuingexpression of the cancer-, organ-, or tissue-specific polypeptides inthe presence of the inflammation mounted against the virus can cause animmune reaction directed against the cancer, thereby causing the cancerto regress.

If the cancer somehow changes and new antigens are subsequentlyexpressed, then the same nucleic acid library or a different nucleicacid library (e.g., a nucleic acid library generated from the changedcancer cells) can be administered to the mammal. In these cases, themammal can develop an immune response against those antigens (e.g.,polypeptides) that are expressed by the changed cancer, thereby causingthe cancer to regress.

In general, one aspect of this document features a method for treatingcancer present in a mammal. The method comprises, or consistsessentially of, administering, to the mammal, a nucleic acid libraryunder conditions wherein nucleic acid members of the nucleic acidlibrary are expressed in the mammal, thereby reducing the number ofviable cancer cells present within the mammal. The mammal can be ahuman. The administration can be an intratumoral or intravenousadministration. The nucleic acid library can be a cDNA library. Thenucleic acid library can be administered to the mammal using a virus.The virus can be an oncolytic virus. The virus can be a vesicularstomatitis virus. The nucleic acid members can be cDNA molecules,wherein each cDNA molecule encodes a polypeptide. The nucleic acidlibrary can comprise a plurality of different nucleic acid members, andwherein each of the plurality of different nucleic acid members canencode a different mammalian polypeptide. The different mammalianpolypeptides can be polypeptides of a member of the same species as themammal. The different mammalian polypeptides can be polypeptides of amember of a different species than the species of the mammal. Thedifferent mammalian polypeptides can be polypeptides of the mammal. Thedifferent mammalian polypeptides can be polypeptides of the cancer. Thedifferent mammalian polypeptides can be polypeptides of an organ ortissue that is an organ or tissue of origin of the cancer. The cancercan be prostrate cancer, and the different mammalian polypeptides can bepolypeptides expressed by prostate cells. The cancer can be lung cancer,and the different mammalian polypeptides can be polypeptides expressedby lung cells. The cancer can be skin cancer, and the differentmammalian polypeptides can be polypeptides expressed by skin cells. Thenucleic acid library can comprise a collection of greater than 10⁴different nucleic acid members, and wherein each of the 10⁴ differentnucleic acid members can encode a different mammalian polypeptide. Thenucleic acid library can comprise a collection of greater than 10⁵different nucleic acid members, and wherein each of the 10⁵ differentnucleic acid members can encode a different mammalian polypeptide. Thenucleic acid library can comprise a collection of greater than 10⁶different nucleic acid members, and wherein each of the 10⁶ differentnucleic acid members can encode a different mammalian polypeptide. Thenucleic acid library can comprise a collection of greater than 10⁷different nucleic acid members, and wherein each of the 10⁷ differentnucleic acid members can encode a different mammalian polypeptide. Thenucleic acid library can be administered to the mammal in combinationwith an adjuvant. The adjuvant can be selected from the group consistingof an HSP70 polypeptide, a vesicular stomatitis virus, BCG, a vacciniavirus, and an adenovirus.

In another aspect, this document features a composition for treatingcancer present in a mammal. The composition comprises, or consistsessentially of, a nucleic acid library comprising a plurality ofdifferent nucleic acid members, wherein each of the plurality ofdifferent nucleic acid members encodes a different mammalian polypeptideand is located within the genome of an oncolytic virus having theability to infect a cell present within the mammal, and wherein themammalian polypeptides are expressed within the mammal followingadministration of the composition to the mammal. The mammal can be ahuman. The administration can be an intratumoral or intravenousadministration. The nucleic acid library can be a cDNA library. Theoncolytic virus can be a vesicular stomatitis virus. The differentmammalian polypeptides can be polypeptides of a member of the samespecies as the mammal. The different mammalian polypeptides can bepolypeptides of a member of a different species than the species of themammal. The different mammalian polypeptides can be polypeptides of themammal. The different mammalian polypeptides can be polypeptides of thecancer. The different mammalian polypeptides can be polypeptides of anorgan or tissue that is an organ or tissue of origin of the cancer. Thecancer can be prostrate cancer, and the different mammalian polypeptidescan be polypeptides expressed by prostate cells. The cancer can be lungcancer, and the different mammalian polypeptides can be polypeptidesexpressed by lung cells. The cancer can be skin cancer, and thedifferent mammalian polypeptides can be polypeptides expressed by skincells. The nucleic acid library can comprise a collection of greaterthan 10⁴ different nucleic acid members, and wherein each of the 10⁴different nucleic acid members can encode a different mammalianpolypeptide. The nucleic acid library can comprise a collection ofgreater than 10⁵ different nucleic acid members, and wherein each of the10⁵ different nucleic acid members can encode a different mammalianpolypeptide. The nucleic acid library can comprise a collection ofgreater than 10⁶ different nucleic acid members, and wherein each of the10⁶ different nucleic acid members can encode a different mammalianpolypeptide. The nucleic acid library can comprise a collection ofgreater than 10⁷ different nucleic acid members, and wherein each of the10⁷ different nucleic acid members can encode a different mammalianpolypeptide. The composition can lack serum.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention pertains. Although methods and materialssimilar or equivalent to those described herein can be used to practicethe invention, suitable methods and materials are described below. Allpublications, patent applications, patents, and other referencesmentioned herein are incorporated by reference in their entirety. Incase of conflict, the present specification, including definitions, willcontrol. In addition, the materials, methods, and examples areillustrative only and not intended to be limiting.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of a gel of a PCR amplified, human prostate cDNAexpression library. A Template Bioexpress plasmid was used to carry thecDNAs.

FIG. 2 contains two graphs plotting the level of IL-17 (pg/mL) or IFN-γ(pg/mL) produced by splenocytes from the indicated mice followingincubation with TC2 cells (E:T ratio=100:1). Vesicular stomatitisviruses containing a human prostate cDNA library are referred togenerally as OSOVIASAL (organ specific oncolytic virus incorporatedaltered specific antigen library). Lanes 1-3 are results fromsplenocytes from mice injected intra-prostatically with PBS. Lanes 4-6are results from splenocytes from mice injected with PBS. Lanes 7-12 areresults from splenocytes from mice injected with VSV-GFP. Lanes 13-18are results from splenocytes from mice injected with OSOVIASAL. Lanes19-21 are results from TC2 tumor cells only.

FIG. 3 is a diagram of an administration protocol for testing the use ofa nucleic acid library to treat cancer.

FIG. 4 is a graph plotting survival curves for mice with subcutaneousTC2 prostate cancer and treated as indicated for Groups A, B, C, D, andE. Each group contained seven mice.

FIG. 5 is a graph plotting the level of IL-17 (pg/mL) produced bysplenocytes from mice treated as indicated following incubation witheither a B16 melanoma lysate (lanes 1, 5, 9, and 13), a TrampC2 prostatetumor lysate (lanes 2, 6, 10, and 14), a normal mouse prostate lysate(lanes 3, 7, 11, and 15), or a normal mouse pancreas lysate (lanes 4, 8,12, and 16). No difference was observed in the level of IFNγ betweenthese groups. it=intratumoral injections; iv=intravenous injections.

FIG. 6 contains photographs (4×) of TC2 tumors following intravenoustreatment with VSV-GFP or OSOVIASAL, which induced tumor regression withminimal signs of autoimmune prostatitis. The TC2 tumors that underwentregression and regrowth in vivo exhibited a very different morphologyfrom VSV-GFP- or control-treated TC2 tumors.

FIG. 7 contains photographs (10×) of TC2 tumors following intravenoustreatment with VSV-GFP or OSOVIASAL, which induced tumor regression withminimal signs of autoimmune prostatitis.

FIG. 8 contains photographs of TC2 tumors following intravenoustreatment with VSV-GFP or OSOVIASAL, which induced tumor regression withminimal signs of autoimmune prostatitis.

FIGS. 9A and 9B contain photographs of TC2 tumors following intravenoustreatment with PBS or OSOVIASAL. Direct intraprostatic injection ofOSOVIASAL induced clinical signs of prostatitis.

FIG. 10 is a diagram of an experiment designed to assess the ability ofOSOVIASAL in combination with recombinant HSP70 to stimulate IL-17release.

FIG. 11 is a graph plotting the amount of IL-17 released (pg/mL) fromsplenocytes and lymph node cells infected with OSOVIASAL in the presenceof recombinant HSP70 following exposure to a prostate cancer cell lysate(TC2 cell lysate; C1), a melanoma cell lysate (B16 cell lysate; C2), anormal mouse prostrate cell lysate (C3), a normal mouse pancreas celllysate (C4), or no lysate (C5).

FIG. 12 is a graph plotting survival curves for mice with subcutaneousB16ova melanoma cancer and treated with OSOVITAL-ova or VSV-GFP.

DETAILED DESCRIPTION

This document provides methods and materials related to the use ofnucleic acid libraries to treat cancer. For example, this documentprovides methods and materials for using nucleic acid libraries toreduce the number of viable cancer cells within a mammal and/or toincrease the survival time of a mammal with cancer. Any type of cancercan be treated such that the number of viable cancer cells within themammal is reduced and/or the survival time of the mammal with cancer isincreased. For example, prostate cancer, skin cancer (e.g., melanoma),lung cancer, breast cancer, pancreatic cancer, and colorectal cancer canbe treated as described herein.

The term “nucleic acid library” as used herein refers to a collection ofnucleic acid molecules where the collection includes at least about 10²different nucleic acid molecules. For example, a nucleic acid librarydescribed herein can include at least about 10², 10³, 10⁴, 10⁵, 10⁶,10⁷, or more different nucleic acid molecules. In some cases, a nucleicacid library used as described herein can be a cDNA library. Forexample, a nucleic acid library can have at least about 10² differentcDNA molecules. Each different cDNA molecule can encode a differentpolypeptide. In general, a nucleic acid library provided herein can bedesigned to express its nucleic acid members (e.g., cDNAs) such that acollection of at least 10² different polypeptides can be produced. Thepolypeptides can be full-length polypeptides as found in the sourcecells used to generate the nucleic acid library or can be portions ofsuch full-length polypeptides. For example, such portions of full-lengthpolypeptides can be polypeptides having greater than 10, 20, 30, 40, 50,60, 70, 80, 90, 100, or more amino acid residues of the full-lengthpolypeptides.

In general, a nucleic acid library (e.g., an expression nucleic acidlibrary) can be obtained from the cancer to be treated or can beobtained from an organ or tissue or cell (organ/tissue/cell) of originof the cancer type to be treated. For example, when treating skin cancer(e.g., melanoma), a cDNA library created from normal skin cells can beused. When treating pancreatic cancer, a cDNA library created fromnormal pancreatic cells can be used. In some cases, a nucleic acidlibrary can be obtained from an embryonic cell or cell line. Anembryonic cell library can provide many tumor associated antigens sincemany tumor associated antigens also are embryonically expressed antigensthat become re-activated for expression in tumor cells. In some cases,vaccination with an embryonic cell nucleic acid library can allow foreffective vaccination over and above that achieved with vaccinationagainst tissue specific antigens.

In some cases, a nucleic acid library can be a collection of at leastabout 10² different nucleic acid molecules of the mammal to be treated(e.g., an autoexpression library) or can be a collection of at leastabout 10² different nucleic acid molecules of a member of the samespecies as the mammal to be treated (e.g., an alloexpression library).For example, when treating lung cancer in human A, normal lung tissuefrom human B can be obtained and used to make a human lung tissue cDNAlibrary that can be administered to human A. In some cases, a nucleicacid library can be a collection of at least about 10² different nucleicacid molecules of a member of a mammalian species that is different fromthe species of the mammal to be treated (e.g., a xenoexpressionlibrary). For example, when treating prostate cancer in a human, normalprostate tissue from a non-human mammal (e.g., a monkey, dog, cat, cow,pig, sheep, goat, mouse, or rat) can be obtained and used to make anon-human mammalian prostate tissue cDNA library that can beadministered to the human.

Any appropriate method can be used to make a nucleic acid library. Forexample, common molecular cloning and PCR techniques can be used to makea cDNA library designed to express the cDNA molecules. Any appropriatemethod can be used to deliver a nucleic acid library (e.g., anexpression nucleic acid library) to a mammal. For example, a nucleicacid library can be delivered as plasmids or can be incorporated intoviruses (e.g., oncolytic viruses such as vesicular stomatitis viruses,vaccinia viruses, or adenovirus viruses), bacteria, or cells that aredelivered to a mammal. Examples of viruses that can be used to delivernucleic acid libraries to mammals having cancer include, withoutlimitation, vesicular stomatitis viruses, adenoviruses, vacciniavirusus, retroviruses, and lentiviruses.

Any appropriate method can be used to administer a nucleic acid libraryto a mammal having cancer. For example, a nucleic acid library can be inthe form of plasmids that are formulated with a pharmaceuticallyacceptable carrier to create a pharmaceutical composition foradministration to a human with cancer. In some cases, a nucleic acidlibrary can be in the form of a population of viruses (e.g., apopulation of vesicular stomatitis viruses) that are formulated with apharmaceutically acceptable carrier to create a pharmaceuticalcomposition for administration to a human with cancer. In these cases,each virus member of the population of viruses can contain a differentnucleic acid member of the nucleic acid library. Examples ofpharmaceutically acceptable carriers include, without limitation,liposomes and other lipids. The pharmaceutical composition can includean adjuvant such as HSP70 polypeptides (GenBank gi nos. 38327039 or38327038), BCG (Bacillus Calmette-Guérin), or Coley's toxin. In somecases, a pharmaceutical composition containing a nucleic acid librarycan lack serum (e.g., bovine serum such as fetal calf serum).

A nucleic acid library (e.g., population of viruses containing thelibrary) or a composition containing a nucleic acid library can beadministered directly to cancer cells (e.g., by intratumoraladministration) or can be administered systemically (e.g., byintravenous, intraperitoneal, intrapleural, or intra-arterialadministration). Any appropriate amount of material can be administeredto a mammal. For example, the amount of material administered to amammal can be large enough to deliver at least one copy of each nucleicacid member of the nucleic acid library. For example, when using alibrary that has 10⁴ nucleic acid members incorporated into viruses,then the total number of viruses administered to the mammal can be rangefrom about 10⁴ to about 10⁸. In some cases, the amount of materialadministered to a mammal can be an amount that is less than the amountneeded to deliver at least one copy of each nucleic acid member of thenucleic acid library. For example, when using a library that has 10⁶nucleic acid members incorporated into viruses, then the total number ofviruses administered to the mammal can be range from about 10⁴ to about10⁵.

The invention will be further described in the following examples, whichdo not limit the scope of the invention described in the claims.

EXAMPLES Example 1—Use of Organ-Specific cDNA Libraries Expressed byOncolytic Viruses to Treat Cancer

cDNA libraries from human prostate tissue and mouse prostate recurrenttumors were amplified by PCR and cloned into vesicular stomatitis virus(VSV) (FIG. 1). Briefly, the cDNA library was amplified with primers toallow for directional cloning into the VSV genome between the Xho1 andNhe1 restriction sites between the G and L genes. Viruses were generatedby co-transfection of Vero cells with the viral helper genes and thevaccinia encoded T7 polymerase. Viruses were harvested from transfectedcells after 48-72 hours, and all the viruses were amplified for one ortwo rounds on Vero cells. Viral titers of 10⁷ to 10⁸ pfu/mL wereobtained (as tittered on BHK cells by limiting dilution assay). Whilenot being limited to any particular mode of action, it is possible thatthe viral-expressed cDNA library may encompass epitopes from most normalantigens that might serve as immunogens for cancer rejection, therebydispensing with the need for direct killing of the normal tissue. Inaddition, the immunogenicity of the VSV itself could serve the role ofan adjuvant.

For this study, a total of 18 mice were used. Three mice were used ineach group (A1, A2, B1, B2, C1, and C2). The A1 and A2 mice wereinjected intra-prostatically with PBS. B1 and B2 mice were injectedintraprostatically with vesicular stomatitis virus designed to expressgreen fluorescent protein (VSV-GFP). C1 and C2 mice were injectedintraprostatically with vesicular stomatitis viruses containing thehuman prostate cDNA library (VSV-Ag). Each mouse was given 50 μL ofvirus diluted in PBS at a final titer of ˜10⁶ virus per injectionintravenously for a total of 6 injections separated by two days each.The mice were sacrificed on day 40-60 after tumor seeding, and theT-cell splenocytes were evaluated for release of IL-17 (interleukin-17)and IFNγ (interferon-gamma) when co-cultured with TC2 tumor cells. Thesecretion of significant levels of cytokine in response to stimulationwith TC2 cells indicated that the splenocytes contained reactive T cellsubsets with specificity for prostate tumor cells. Only the splenocytesfrom mice injected with VSV-Ag exhibited reactivity to the TC2 murineprostate cancer cells (FIG. 2).

In an in vivo study, 35 mice were injected with TC2 prostate cancercells subcutaneously (sc) on day one. When the sc prostate cancer waspalpable, at about day 7, the mice were divided into five groups (A, B,C, D, and E) of mice with seven mice in each group, and the followinginjections were performed (FIG. 3): intratumoral injection of VSV-GFP(Group A), intratumoral injection of VSV-Ag (OSOVIASAL of the humanprostate antigen library; Group B), intratumoral injection of VSV-GFP HI(heat inactivated; Group C), intravenous injection of VSV-Ag (Group D),and intravenous injection of VSV-GFP (Group E). Injections wereperformed every two days for a total of six injections. The mice wereevaluated for survival and autoimmunity, and at the time of sacrifice,the T cells (splenocytes) were evaluated for reactivity via release ofIL-17 and IFNγ.

Kaplan-Meyer survival curves revealed a marked difference in survival inGroups B and D (VSV-Ag given either intratumorally or intravenously)than for the other groups (FIG. 4). The 50% survival time was about 20days for the other groups, while it was about 40 days for Group B(intratumoral VSV-Ag) and about 50 days for Group D (VSV-Ag iv).Histology of the tumors revealed marked tumor regression in Groups B andD with minimal signs of autoimmune prostatitis (FIGS. 6-9).

Reactivity of the splenocytes from four mice each from Group A, Group B,Group D, and Group E were tested against B16 melanoma lysate targets,TC2 protstate tumor lysate targets, normal mouse prostate lysatetargets, and normal mouse pancreas lysate targets. Only Group Dexhibited reactivity to TC2 lysate with release of IL-17 (FIG. 5). Theseresults demonstrate that an altered self-antigen expression via virusesexpressing a nucleic acid library can cause reaction to the cancer butnot to normal tissues or other cancers. These results also demonstratethat expression of nucleic acid libraries can be used to treat cancer(e.g., prostate cancer).

In summary, injection (e.g., intravenous) of VSV encoding a cDNA libraryfrom normal prostate resulted in regression of murine prostate tumors inimmune competent mice. The regressions were immune mediated, as opposedto induced by viral oncolysis. Transient inflammation was observed inthe normal prostate, but no evidence of long term autoimmunity wasapparent. Mice in which tumors were rejected developed potent Th17responses against prostate tumor cells, as well as normal prostatetissues. Moreover, tumors which initially regressed, but were not cured,recurred aggressively, with a markedly different histologicalappearance, and antigenic profile, to the initially implanted tumorcells, suggesting that the cDNA library-mediated vaccination imposed astringent immune selection upon tumors. This approach dispensed with theneed to induce direct damage to normal tissues in situ, allowed forwide-ranging in vivo immune selection for antigens that are likely to beeffective targets for both autoimmune and anti-tumor responses, andestablished the use of viruses (e.g., oncolytic viruses) as immuneadjuvants for the immunotherapy of cancer. The results provided hereinfurther demonstrate that combining induction of autoimmune reactivityagainst normal tissue-specific antigens (e.g., polypeptides) with highlyimmunogenic, viral adjuvant-induced antigen presentation can be asuccessful cancer immunotherapy.

Example 2—Use of a Heat Shock Protein, HSP70, in Combination withOrgan-Specific cDNA Libraries Expressed by Oncolytic Viruses to TreatCancer

Vesicular stomatitis viruses containing a cDNA library from humanprostate tissue (OSOVIASAL of the human prostate antigen library) wasused in combination with recombinant HSP70 (Sigma-Aldrich, St Louis,Product #H7283) to assess the combination's ability to increase IL-17responses. Briefly, pooled lymph node cells and splenocytes from C57BL/6mice were plated 10⁶ cells per well. After an incubation, the cells wereinfected with the vesicular stomatitis viruses containing the cDNAlibrary from human prostate tissue (MOI=1) in the presence of 10 μg/mLof recombinant HSP70. 72 and 144 hours after the initial plating,additional cells (10⁶ cells per well) were added to each well (FIG. 10).In addition, 72 and 144 hours after the initial infection, additionalinfections in the presence of recombinant HSP70 were carried out (FIG.10). 72 hours after the third infection, the cells were incubated with(a) a prostate cancer cell lysate (TC2 cell lysate), (b) a melanoma celllysate (B16 cell lysate), (c) a normal mouse prostrate cell lysate, (d)a normal mouse pancreas cell lysate, or (e) no lysate, for 48 hours.After the 48-hour incubation, the cells were assessed by ELISA for IL-17release. Lysates from prostate cancer cells and normal prostate cellscaused a marked IL-17 response in splenocytes as compared to theresponse measured for cells exposed to the other lysates (FIG. 11).These results demonstrate that the addition of HSP-70 to VSV expressingcDNAs to prostate increased the IL-17 autoimmune response to both tumorand normal organ tissues.

Example 3—Use of a Tumor-Specific cDNA Library Expressed by OncolyticViruses to Treat Cancer

A cDNA library was made using nucleic acid from mouse B16ova melanomatumor cells and cloned into vesicular stomatitis virus (VSV). The VSVlibrary was designated OSOVITAL-ova.

In an in vivo study, C57BL/6 mice were injected with B16ova melanomatumor cells subcutaneously (sc) on day one. When the subcutaneousmelanoma cancer was palpable, the mice were divided into two groups(OSOVITAL-ova and VSV-GFP) of mice with seven mice in each group, andthe following injections were performed: intratumoral injection ofOSOVITAL-ova and intratumoral injection VSV-GFP. Injections wereperformed every two days for a total of six injections. The mice wereevaluated for survival.

Kaplan-Meyer survival curves revealed a marked difference in survivalfor mammals treated with OSOVITAL-ova as compared to mammals treatedwith VSV-GFP (FIG. 12). These results demonstrate that cDNA librariesfrom cancer cells constructed in a virus such as VSV can inducesignificant responses against cancer cells present within a mammal.

OTHER EMBODIMENTS

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

What is claimed is:
 1. A method for treating pre-existing cancer presentin a mammal, wherein said method comprises administering, to saidmammal, a nucleic acid library under conditions wherein nucleic acidmembers of said nucleic acid library are expressed in said mammal,wherein the number of viable cancer cells present within said mammal isreduced following said administrating step and the survival time of saidmammal is increased as compared to a comparable mammal not administeredsaid nucleic acid library, wherein said nucleic acid library comprises aplurality of different nucleic acid members, and wherein each of saidplurality of different nucleic acid members encodes a differentmammalian polypeptide.
 2. The method of claim 1, wherein said mammal isa human.
 3. The method of claim 1, wherein the different mammalianpolypeptides are polypeptides of a member of the same species as saidmammal.
 4. The method of claim 1, wherein the different mammalianpolypeptides are polypeptides of said mammal.
 5. The method of claim 1,wherein said nucleic acid library is a vesicular stomatitis viralnucleic acid library of said different nucleic acid members.
 6. Themethod of claim 1, wherein said nucleic acid library is an adenoviralnucleic acid library of said different nucleic acid members.
 7. Themethod of claim 1, wherein said nucleic acid library is a normal cellnucleic acid library.